Study protocol: NITric oxide during cardiopulmonary bypass to improve Recovery in Infants with Congenital heart defects (NITRIC trial): a randomised controlled trial

INTRODUCTION

Congenital heart disease (CHD) is a major cause of infant mortality. Many infants with CHD require corrective surgery with most operations requiring cardiopulmonary bypass (CPB). CPB triggers a systemic inflammatory response which is associated with low cardiac output syndrome (LCOS), postoperative morbidity and mortality. Delivery of nitric oxide (NO) into CPB circuits can provide myocardial protection and reduce bypass-induced inflammation, leading to less LCOS and improved recovery. We hypothesised that using NO during CPB increases ventilator-free days (VFD) (the number of days patients spend alive and free from invasive mechanical ventilation up until day 28) compared with standard care. Here, we describe the NITRIC trial protocol.

METHODS AND ANALYSIS

The NITRIC trial is a randomised, double-blind, controlled, parallel-group, two-sided superiority trial to be conducted in six paediatric cardiac surgical centres. One thousand three-hundred and twenty infants <2 years of age undergoing cardiac surgery with CPB will be randomly assigned to NO at 20 ppm administered into the CPB oxygenator for the duration of CPB or standard care (no NO) in a 1:1 ratio with stratification by age (<6 and ≥6 weeks), single ventricle physiology (Y/N) and study centre. The primary outcome will be VFD to day 28. Secondary outcomes include a composite of LCOS, need for extracorporeal membrane oxygenation or death within 28 days of surgery; length of stay in intensive care and in hospital; and, healthcare costs. Analyses will be conducted on an intention-to-treat basis. Preplanned secondary analyses will investigate the impact of NO on host inflammatory profiles postsurgery.

ETHICS AND DISSEMINATION

The study has ethical approval (HREC/17/QRCH/43, dated 26 April 2017), is registered in the Australian New Zealand Clinical Trials Registry (ACTRN12617000821392) and commenced recruitment in July 2017. The primary manuscript will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ACTRN12617000821392.

Estimating the extra cost of living for people with disabilities

Addressing the extra economic costs of disability is a logical step towards alleviating elements of social exclusion for people with disabilities. This study estimates the long-run economic cost of disability in Ireland in terms of the additional spending needs that arise due to disability. It defines and estimates models of the private costs borne by families with individuals who have a disability in Ireland when compared with the wider population, both in general and by severity of disability. Our modelling framework is based on the standard of living approach to estimating the cost of disability. We extend on previous research by applying panel ordered probit models to living in Ireland survey data 1995-2001 in order to control for the effects of previous disability and income and correlated unobserved heterogeneity. The approach allows us to quantify, for the first time, the additional long-run economic costs of living associated with disability. Our findings suggest that the extra economic cost of disability in Ireland is large and varies by severity of disability, with important implications for measures of poverty.

Method for bacteriophage isolation against target Campylobacter strains

AIMS

Poultry meat is considered a major source of Campylobacter. This micro-aerobic bacterium is commonly responsible for foodborne illness. This work focuses on the isolation of Campylobacter coli lytic bacteriophages (phages) against target C. coli strains.

METHODS AND RESULTS

A method involving the enrichment of free-range chicken samples in a broth containing the target C. coli strains and salts (CaCl(2) and MgSO(4)) was used for phage isolation. This method allowed the isolation of 43 phages that were active against 83% of the C. coli strains used in the isolation procedure. Approximately 65% of the phages were also effective against Campylobacter jejuni strains.

CONCLUSIONS

The use of target pathogens in the phage isolation step improves the likelihood of detecting and isolating phages for the control of these specific strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This technique will be valuable in the context of phage therapy for enriching for phages that are active against specifically identified strains of bacteria, for example from a food poisoning outbreak or epidemic strains resistant to multiple antibiotics. In these situations, using the conventional methods for searching for bacteriophages active for these particular strains can be a time-consuming, if not an unsuccessful process. Using the isolation method described in this manuscript, the particular strains can be added to the enrichment broth increasing the probability of finding phages against them. Therefore, it will shorten the time needed for seeking phages able to lyse target strains, which in most of the cases, because of the rapid increase in antimicrobial-resistant bacteria, is of crucial importance.

Economic consequences of falls and fractures among older people

This paper uses a burden of illness methodology to achieve a better understanding of the cost of falls and fractures within Ireland. The base number of older people falling annually in Ireland is 130,000. About 80% of these are non-injurious with the remainder following a healthcare trajectory that may involve hospital care, GP visits, outpatient visits, informal care, long-stay care and sometimes death. Unit costs are applied to the different levels of care and aggregated to generate the overall cost of illness of falls and fractures in the country. The estimated baseline cost of falls and fractures is Euro 404 million. The largest components of this cost are: mortality, lost quality of life, long-stay care costs and hospital inpatient costs. The findings are relevant in the context of the development of a National Strategy for the prevention of falls and fractures in Ireland. Investment in such a Strategy will likely yield significant benefits.

The phosphorus budget of the Thame catchment, Oxfordshire: 2. Modelling

The phosphorus budget of the River Thame was modelled at a daily time scale, using estimates of diffuse and point source contributions of discharge. The model simulated suspended sediment (SS), soluble unreactive phosphorus (SUP), soluble reactive phosphorus (SRP) and particulate phosphorus (PP) concentrations within the main river and major tributaries. Diffuse source estimates of phosphorus loads were based on characteristic losses from identified main landscape classes, with hydrology described by a simple conceptual storage model. In-stream flow was modelled using a kinematic wave equation. Transfer of suspended sediment and phosphorus components was approximated by advection. In-stream sources and sinks included uptake and release of soluble reactive phosphorus by bed sediment, instant equilibration between SRP and the PP concentration on suspended sediment, and flow-related entrainment and deposition of suspended sediment. Simulations at sites within the catchment were compared with measurements made in 1998-1999. Results showed the P budget is dominated by mixing of diffuse and point source water, but some within-river processes have been shown to be capable of significantly influencing SRP concentrations. The development of a sediment entrainment and deposition component of the model has proved particularly valuable in emulating the hysteretic relationship between discharge and suspended sediment concentration in the river. It also provides a measure of available bed sediment.

The phosphorus budget of the Thame catchment, Oxfordshire, UK: 1. Mass balance

The relative magnitudes of annual diffuse and point source loads of phosphorus (P) to the River Thame were estimated from daily and monthly measurements of discharge and concentration. Existing data from gauging and monitoring sites on the river network and at point sources were supplemented by survey data at a range of spatial scales. Results showed that during low flow periods most of the P could be attributed to point sources, while at high flows the figure was less than 10%. The introduction of P stripping at Aylesbury, a major sewage treatment works in the catchment, was estimated to have reduced the annual load of P from the sewage treatment works by approximately 45 t, with a similar reduction in loss from the catchment. This gave a reduction in low flow concentrations of soluble reactive phosphorus (SRP) from 2.5 to 1.7 mg l(-1). Concentrations of SRP in river water remain above eutrophication thresholds because of the influence of other STWs in the catchment and insufficient natural discharge to dilute this.

Changes in intrafollicular pressure in the rat ovary by nitric oxide and by alteration of systemic blood pressure

BACKGROUND

ovulation is associated with degradation of the follicular apex vasodilatation and increased permeability of ovarian vessels. These changes may maintain or increase intrafollicular pressure (IFP) at ovulation to cause rupture of the follicular wall.

OBJECTIVE

to investigate the possible regulation of IFP during the ovulatory process.

STUDY DESIGN

immature Sprague-Dawley rats were primed with pregnant mare serum gonadotrophin (PMSG; 10IU) and given hCG (10IU) 48h later. The ovary was exposed 48-60h after PMSG, micropipette inserted into the Graafian follicle and the IFP measured at three time periods: preovulatory (PO) 48h after PMSG; midovulatory (MO) 4-7h after hCG; late ovulatory (LO) 9-12h after hCG. The offset of the nitric oxide synthase (NOS) inhibitor L-arginine methyl ester (L-NAME), the alpha(1)-adrenoceptor agonist phenylephrine and the beta-adrenoceptor agonist isoprenaline were tested.

RESULTS

phenylephrine given i.v. increased the systemic blood pressure, and significantly decreased the IFP in the LO phase (78% of pre-treatment value). Local administration of phenylephrine or isoprenaline (1ml of 1.5-15 microM) by superfusion over the ovary did not change the IFP. Local administration of L-NAME (1ml of 2 microM) significantly lowered (P<0.05) the IFP in the MO and LO phases, but was without effect in the PO phase.

CONCLUSION

this study reveals that IFP regulation may be related to changes of the systemic blood pressure and that NO may be one local ovarian mediator in IFP regulation.

Effect of carbon dioxide on the Oriental cockroach Blatta orientalis

Exposure to high concentrations of carbon dioxide (CO2) killed adult and nymphal stages of the oriental cockroach Blatta orientalis L. (Dictyoptera: Blattidae) with LT50 values of 11.5-16.2 h for 60% CO2 in air and 5.7-7.1 h for 100% CO2 at 20 degrees C; corresponding LT50s at 28 degrees C were 2.8-4.6 h for 60% CO2 in air and 2.3-3.6 h for 100% CO2. Complete kill of mobile stages was obtained within 24 h using 60% CO2 at 20 degrees C. Survivors of treatments with 100% CO2 at 28 degrees C remained completely paralysed for up to 3 days post-treatment and took up to 5 days to regain normal movement, but adult females then resumed production of oothecae with no significant loss in fecundity. Oothecae 5 or 30 days after deposition required 60-84 h exposure to 60% CO2 at 20 degrees C to prevent emergence of nymphs but less time using 100% CO2 at 28 degrees C. At 28 degrees C, when adult females were treated with 100% CO2 and 52% r.h. for 6 h (giving 100% mortality) loss of weight was significantly greater than that following treatment with air at 52% r.h. for 6 h (giving no mortality). However, significantly greater weight loss also occurred when they were treated with dried air (< 10% r.h.) for 6 h, also with no mortality. The toxicity of CO2 to mobile stages of the oriental cockroach appeared to result from irreversible effects on the nervous system, rather than from water loss during exposure.

Novel method for intrafollicular pressure measurements in the rat ovary: increased intrafollicular pressure after hCG stimulation

The ovulatory process in the rat comprises a period of about 12-15 h, from the time of the preovulatory LH surge to follicular rupture and extrusion of the oocyte. Follicular rupture is most likely caused, at least in part, by decreased tensile strength at the follicular apex due to degradation of collagen fibres of the extracellular matrix. It has been debated whether changes in intrafollicular pressure occur during the ovulatory process and whether such changes facilitate rupture of the follicle. In the present study, rats were primed with equine chorionic gonadotrophin (eCG, 10 iu) followed by hCG (10 iu) 48 h later. The intrafollicular pressure in the preovulatory follicle was recorded during 1 h at distinct time phases of the ovulatory process by use of an active servo-null pressure system based on the proportionality between electrical resistance and pressure within the tip of an inserted micropipette. The basal intrafollicular pressure was 16.6 +/- 1.0 mm Hg at the preovulatory phase (48 h after eCG) and increased gradually throughout the ovulatory process to 21.4 +/- 2.4 mm Hg at 4-7 h after hCG (mid-ovulatory phase) and 23.9 +/- 1.9 mm Hg at 8-12 h after hCG (late ovulatory phase; significantly higher (P < 0.01) than the preovulatory phase). Short-term peaks of increased pressure, possibly representing contractility, were not detected in follicles of the preovulatory phase, but were seen in most follicles of the mid- and late ovulatory phases. The mean amplitude of the short-term pressure increases was 12.3 +/- 3.2 mm Hg and the increases occurred at intervals of 24.7 +/- 3.6 s. These short-term increments in intrafollicular pressure were still present after hysterectomy had been performed. The wall tension index was calculated by measuring the follicular size and estimating the thickness of the follicle wall. The index increased from 93.9 +/- 13.3 at the preovulatory phase to 207.3 +/- 47.7 (mid-ovulatory phase) and to significantly higher values at the late ovulatory phase (320.9 +/- 33.5). In conclusion, this study shows that there is an increase in intrafollicular pressure in the ovulating follicle of the rat ovary during the late stages of the ovulatory process, and that short-term increases in intrafollicular pressure occur during the late phase of the ovulatory process. These changes in pressure may be essential for follicular rupture to proceed normally.

Recruiting problem-based learning (PBL) tutors for a PBL-based curriculum: the Flinders University experience

OBJECTIVES

To examine the contribution made to problem-based learning (PBL) by individual teachers and by departments in years 1 and 2 of a new graduate-entry medical programme (GEMP) with a PBL-based curriculum.

METHODS

We compiled a database on all PBL tutoring undertaken in years 1 and 2 during the first 3 years in which the GEMP was delivered. This allowed us to quantify and analyse the contribution made by individuals and by departments.

RESULTS

At 3 years following introduction of the GEMP, 136 (25.9%) of the school's 525 staff had trained as PBL tutors and 98 (18.7%) had tutored. Both individuals and departments differed greatly in the amount of time devoted to PBL tutoring. Staff who tutored once tended to tutor again in subsequent years. Compared with staff in clinical departments, those in non-clinical departments (who constituted 12% of the total) made a greater relative contribution though a smaller absolute contribution to tutoring.

CONCLUSIONS

These findings prompted us to develop a formula that distributes the PBL tutoring load more evenly across departments. This was successfully introduced in 1999. It recognizes the fact that only a minority of staff will volunteer to become PBL tutors. Strategies that might encourage more staff to tutor are briefly discussed.

The immunohistochemical response of the rat periodontal ligament endothelium to an inflammatory stimulus

Recently, inflammation has been recognised as an important co-requisite to orthodontic tooth movement. When such a reaction is initiated, the process of up-regulation of certain adhesion molecules may occur, resulting in the extravasation of leukocytes. This may stimulate progenitor/precursor pathways and signals that regulate the biological responses resulting in tooth movement. We propose that up-regulation of leukocyte adhesion molecules occurs in response to orthodontic forces, resulting in circulating monocyte attraction, extravasation and differentiation into osteoclasts, which are responsible for bone resorption that results in orthodontic tooth movement. To investigate this hypothesis, it is necessary to determine whether periodontal ligament (PDL) endothelium responds to inflammatory stimuli as other organs do. We studied the normal distribution of endothelial adhesion molecule ICAM-1 within PDL vessels, and then the following exposure to an inflammatory endotoxin. The rat PDL blood vessels expressed ICAM-1 in response to the inflammatory stimulus, similar to other organs, suggesting that the inflammatory responses are similar. Whether and where in the PDL microvascular bed orthodontic forces cause up-regulation of ICAM-1 needs to be established.

Do African Americans have lower energy expenditure than Caucasians?

OBJECTIVE

To review current studies that examine differences in energy expenditure between African Americans and Caucasians as possible modulators of attained differences in overweight status.

DESIGN

Literature review of recent clinical and laboratory studies.

METHODS

Studies chosen for review were those that examined directly resting metabolic rate (RMR), using indirect calorimetry, and total daily energy expenditure (TDEE) and physical activity energy expenditure (PAEE), using doubly labeled water.

RESULTS

Ten of 15 studies reviewed reported a lower RMR in African Americans than in Caucasians. The differences in RMR between African Americans and Caucasians ranged from 81 to 274 kcal/day and could not be explained by differences in age, fat-free mass (FFM) or methodological concerns. Two of six studies of energy expenditure using doubly labeled water suggest that Black adults have a tendency for lower TDEE that can be accounted for primarily by a lower PAEE.

CONCLUSIONS

If future studies indicate conclusively that African Americans do have lower RMR, TDEE and PAEE than Caucasians, then the disproportionally higher risk of obesity and associated metabolic disorders in Black adults may be preventable-especially in Black women. If these race differences are indeed a result of both physiological and behavioral factors, then interventions designed to reduce caloric intake and/or increase energy expenditure through lifestyle activity or structured exercise programs become especially important for African Americans and should be encouraged. International Journal of Obesity (2000)24, 4-13

Vascularization of the pineal complex in the lizard Tiliqua rugosa

The vascularization of the pineal complex in the lizard Tiliqua rugosa was investigated by vascular corrosion and latex casting techniques. The fine structure of the pineal capillaries was also studied by transmission electron microscopy. The pineal complex in T. rugosa consists of an elongated pineal gland proper and a separate, distinct parietal eye. The pineal complex derives an abundant blood supply from branches of the middle and posterior cerebral arteries. Scanning electron microscopy of vascular corrosion casts revealed a dense and extensive pineal capillary bed which drains ultimately into a wide longitudinal sinus suggesting an efficient pathway for the rapid removal of substances secreted by the gland. The parietal eye, which receives a unilateral left-sided blood supply from the unpaired anterior pineal artery, is shown to be a highly vascularized structure. The close morphological relationship between the pineal gland and dorsal sac, where the two structures apparently share the same blood vessels, suggests a functional relationship between them. The pineal capillaries are fenestrated with tight junctions between adjoining endothelial cells. Podia-like abluminal extensions of the endothelial cells were observed in close relation to unmyelinated nerve bundles. The basal margin of the pineal parenchyma is highly invaginated with thin finger-like cytoplasmic protrusions into the pericapillary space. Distinct bands of microfibrils form "struts" anchoring the pineal parenchyma to the endothelial wall. These features may have a role in the transfer of materials between the pineal gland and the blood stream.

Regional cycles of perfusion and non-perfusion in the lung of the term fetal rabbit

The spatial distribution of pulmonary blood flow and its change over time was investigated in term fetal rabbits, using the plasma tracer fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA). A tracer bolus was injected intravenously and allowed to circulate in vivo for increasing periods of time (2-30 minutes) prior to arrest of the circulation and tissue preparation. Initially, fluorescence was present in the vasculature of 43% of lung parenchymal tissue, disposed as discrete regions or "lobules." Interspersed regions of lung tissue received no tracer inflow. With increasing tracer circulation times (10, 20, and 30 minutes), a greater percentage of lung cross-sectional area contained vessels exhibiting tracer fluorescence (64, 96, and 100%, respectively). In the fetal lung, a high pulmonary vascular resistance (PVR) is maintained. Our studies indicate that, at any given moment, fetal pulmonary blood flow is distributed only to a proportion of discrete lung "lobules," while interspersed "lobules" receive no flow at all. The "lobules" alternate between these "high" and "low" vascular resistance states with a periodicity of approximately 35 minutes, comprising 22 minutes of non-perfusion followed by 13 minutes of perfusion. This circulatory pattern permits both the maintenance of high PVR and uniform lung development. Further, by directing flow to only a portion of the vasculature, greater microvascular flow rates are achieved and hence the risk of blood sludging and stasis is reduced. Recruitment of these "non-perfused" regions at birth could thus produce a significant reduction in PVR.

Microvascular Geometry in the Brain of the Lizard Trachydosaurus-Rugosus

The vasculature and microvasculature in the central nervous system of the lizard Trnchydosaurus rugosus was examined by means of scanning electron microscopy of vascular corrosion casts. The arterial supply to the brain is from paired internal carotids. Secondary branches from these feeder arteries form a network over the surface of the lizard brain, giving rise to artery-vein vessel pairs. The vessel pairs bend at right angles to the brain surface, giving rise to terminal arteriole-venular pairs which penetrate the brain substance. Capillaries arise at fairly regular intervals along the vessel pairs, each originating from the arteriole and terminating in the venule at a site contiguous with its origin from the arteriole. In this way all of the capillaries in the central nervous system of the lizard form countercurrent loops. Anastomotic connections between arteriole-venular pairs do not occur, each arterial vessel being an end artery.

Organization of the Vascular Supply to the Brain of the Toad Bufo-Marinus

The vasculature of the brain of the cane toad, Bufo marinus, was studied by means of scanning electron microscopy of vascular corrosion casts. The sole arterial supply to the brain is from branches of the internal carotids. The forebrain is supplied by several branches from the rostra1 ramus of the carotids; the caudal ramus gives rise to a single branch which supplies the mesencephalon and cerebellum. The caudal rami fuse to form a single basilar artery which supplies the medulla. The vascular supply to the choroid plexus of the third ventricle is arterial; the vascular supply to the choroid of the fourth ventricle is entirely venous. Microvascular geometry in the toad brain is specific to the region of the brain examined, ranging from simple long capillaries with few anastomotic connections to much shorter, highly convoluted capillaries with many anastomotic connections.

Functional organization of cerebral microvasculature in a marsupial, the northern quoll (Dasyurus hallucatus)

Capillaries within the central nervous system (CNS) of eutherian mammals form meshworks with numerous anastomoses, whereas capillaries in the CNS of marsupials consist entirely of hairpin-like loops, without anastomotic interconnections. Counter-current blood flow in capillary loops may have been important in the evolutionary development of a cerebral vascular supply. However, loops are not found in eutherian mammals, perhaps because of a limited benefit to the diffusive conductance of gases.

Changes in the spatial distribution of pulmonary blood flow during the fetal/neonatal transition: an in vivo study in the rabbit

The spatial distribution of pulmonary blood flow was investigated in term fetal and neonatal rabbit littermates, using the plasma tracer fluorescein-isothiocyanate bovine serum albumin (FITC-BSA). A tracer bolus was injected intravenously and allowed 2 minutes to circulate in vivo, prior to arrest of the circulation and tissue preparation. In the fetus, fluorescence was only present in 43% of the lung volume, contained within discrete regions of "lobules." Some 57% of lung volume received no tracer inflow at all (during 2 min). In the fetal lung, the size of the potential airspaces in the perfused regions was 1.5 times larger than those in the nonperfused regions. In the fetus, a high pulmonary vascular resistance (PVR) is maintained. It is generally accepted that pulmonary blood flow in the fetus is evenly distributed to the entire vascular bed. Our results show that fetal pulmonary blood flow is distributed to discrete "lobules," while (over a 2 min period) the majority of "lobules" receive no flow at all. Thus, by directing flow to a lesser proportion of the vasculature, greater flow rates are achieved, and the risk of blood sludging and stasis is reduced. Alternation of perfusion with nonperfusion in each "lobule," perhaps regulated by the lobular arterioles, would permit both maintenance of the high fetal PVR and uniform lung development. In the neonatal lung, the plasma tracer was distributed uniformly to the entire vascular bed. This suggests that some of the reduction in PVR at birth is due to recruiting 50-60% of lung vasculature.

Protective effects of the synthetic prostaglandin enprostil on the gastric microvasculature after ethanol injury in the rat

The effect of pretreatment with the synthetic prostaglandin E2 analogue enprostil on ethanol damage to the rat gastric mucosa was studied. Microvascular casts were prepared and studied by scanning electron microscopy. The permeability of mucosal capillaries to fluorescein isothiocyanate-labeled albumin (FITC-albumin) given intravenously was examined by fluorescence microscopy. After administration of ethanol (1 ml absolute ethanol intragastrically) alone, casts showed gross disruption of the normal structure, with large foci of loss of the patency of the capillary network, frequently extending to the level of the submucosal vessels. There was exudation of casting material into the mucosal interstitium and onto the surface of the cast. After administration of FITC-albumin, there was a marked increase in interstitial fluorescence throughout the full thickness of the mucosa. Pretreatment with enprostil (1 microgram/kg intragastrically) prevented most of the damaging effects of ethanol. Increased microvascular permeability to FITC-albumin was noted only in the most superficial layers of the mucosa. These studies characterize the effect of ethanol on the gastric microvasculature and indicate that pretreatment with enprostil restricts this damaging effect to the superficial mucosal microvessels. These studies further suggest that microvascular damage is an early event in ethanol injury, apparently preceding epithelial erosion.

Mucosal microvascular organization of the rat colon

The mucosal microvascular architecture of the rat colon is described from vascular casts and intravital microscopy. Arterial break-up into the mucosal capillary bed invariably occurs at the submucosal/mucosal interface. The mucosal capillaries drain into venules only at the opposing, luminal aspect, i.e., mucosal venules transverse the mucosa without receiving further capillary tributaries. Intravital microscopy of luminal flow confirmed cast predictions. Further, capillary flow was unusually unidirectional, i.e., rarely static or reversible. The possible functional importance of this particular microvascular architecture to water absorption in the colon is discussed.

Mucosal microvascular architecture of the fundus and body of human stomach

Vascular casts of human oxyntic mucosa, examined by scanning electron microscopy, revealed that (a) arterial breakup occurs only at the submucosal aspect of the mucosa, there being no arterial vessels further into the mucosa and (b) mucosal capillaries drain into the infrequent mucosal venules only in the most luminal region of the lamina propria immediately underlying the surface mucus cells; the mucosal venules do not receive capillary tributaries deeper within the mucosa. Thus, blood flow in the mucosal exchange vessels can only occur in a unidirectional fashion, from the serosal to the luminal aspect. Using transmission electron microscopy, an often intimate association was seen between the fenestrated mucosal capillaries and parietal cells. These findings are together incorporated into a hypothesis that proposes vascular transport of HCO3-, released interstitially by secreting parietal cells, from deep within the mucosa toward the surface epithelium, thereby assisting gastric mucosal defense against luminal acid.

The microvasculature of rat salivary glands. A scanning electron microscopic study

The blood vessels together with the parenchymal components of rat salivary glands were studied by scanning electron microscopy (SEM) after removal of stromal connective tissue by acid hydrolysis plus enzymatic digestion. The three-dimensional vascular architecture was also studied by SEM of vascular corrosion cats. Each cluster of 4-5 polymorphous acini is connected with the convoluted duct via an intercalated duct. The convoluted duct usually has a sigmoid course and drains to the intralobular striated duct (about 20 microns in diameter); this has a rather straight course before connecting with the interlobular excretory duct. Myoepithelial cells with radiating processes were observed on the stromal surface of the secretory acini. Pericytes with longitudinal and circular processes were also observed surrounding the stromal surface of capillaries. The acini and convoluted ducts are surrounded by plexuses of capillaries derived from terminal arterioles which run along the intralobular duct system. The sinusoidal capillary plexus enveloping the striated duct receives blood from capillaries surrounding the acini and convoluted ducts through portal venules. The interlobular excretory ducts are richly supplied by a subepithelial network of capillaries which receive blood directly from the interlobular artery and drain into the interlobular vein. Thus, the excretory duct circulation is separated from the intralobular circulation. No arterio-venous anastomoses were observed in the gland. However, veno-venous and arterio-arterial anastomoses were often seen along the excretory duct; such anastomoses may participate in controlling the direction of blood flow through the vascular plexus around the excretory duct. The well-developed subepithelial plexus of capillaries observed around this duct is appropriate for its known absorptive/secretory functions. The capillary network around the acini is densest in the parotid gland and sparsest in the sublingual gland. The subepithelial capillary network of the excretory ducts of the submaxillary gland is denser than those of the other two glands which had similar densities.

The microvascular architecture of the glandular mucosa of rat stomach

The circulatory pattern in the gastric mucosa of the rat and relationships of mucosal capillaries to gastric gland cells were investigated. Techniques used included the vascular corrosion cast/scanning electron microscope method, scanning electron microscopy of acid-digested tissues, conventional transmission electron microscopy and in vivo light microscopy. Arterial break-up into capillaries invariably occurs around the base of the gastric glands. The mucosal capillaries are fenestrated and vesiculated, and pass in close proximity to the abluminal aspects of the cells of the gastric glands, particularly the parietal cells. At the apices of the glands, the capillaries form a honeycomb network closely applied to the abluminal aspect of the surface epithelial cells, before draining into infrequent venules which are embedded in a substantial connective tissue sheath. No capillary drainage occurs into these venules deeper in the mucosa. No evidence of either mucosal or submucosal arteriovenous anastomoses was found. Because of the close proximity of the fenestrated mucosal capillaries to the parietal cells and surface epithelial cells and the direction of capillary blood flow, the alkaline tide of the actively secreting parietal cell must be transferred to the abluminal aspect of the surface epithelial cells. The capacity of these cells to secrete HCO3- or to neutralize back diffusing H+ ions would thereby be increased.

Effects of long term denervation on smooth muscle of the chicken expansor secundariorum

Denervation of the expansor secundariorum muscle of the adult and 2 week chicken, by sectioning the brachial plexus, resulted in an approximate twofold increase in dry weight over 8 weeks. Unlike skeletal muscle, no ultrastructural changes were exhibited by the smooth muscle cells for a period of up to 5 months post denervation. No evidence of hypertrophy of the individual muscle cells was observed, but following colchicine treatment a definite increase in the number of mitotic figures was noted within muscle bundles indicating that the increase in dry weight of the expansor muscle is due to hyperplasia of the smooth muscle cells. The results are discussed in relation to in vitro studies of the interaction of sympathetic nerves with smooth muscle.